Recently, efforts to prepare olefins from methanol have become increasingly important. Methanol can be readily produced from coal, via coal gasification and the production of synthesis gas, with the aid of well-tried technology. If it were possible to convert methanol to lower olefins in an economical manner, the further processing methods which are conventional in the chemical industry today and employ coal as a raw material, could also be preserved. In the past few years, processes have, therefore, been developed with the object of preparing olefins from methanol, dimethyl ether or mixtures thereof.
U.S. Pat. Nos. 3,894,106 (Chang, et al.), 3,894,107 (Butter, et al.) and 3,907,915 (Chang, et al.), respectively, disclose the conversion of alcohols, ethers, carbonyls, or mixtures thereof to olefinic and aromatic hydrocarbons by contact with a catalyst comprising a crystalline aluminosilicate zeolite having a silica-to-alumina ratio of at least about 12 and a Constraint Index of about 1 to 12.
The conversion of methanol and dimethyl ether to olefinic and aromatic hydrocarbons is described in U.S. Pat. No. 3,911,041 (Kaeding, et al.).
German Laid-Open Application DOS No. 2,615,150 [from 4,503,281 (Hoelderich, et al.)]relates to a process for the preparation of olefins from a methanol feed using a ZSM-5 aluminosilicate zeolite.
U.S. Pat. No. 4,361,715 (short, et al.) relates to the catalytic conversion of lower molecular weight oxygenates to olefins over a bed of aluminosilicate zeolite catalyst. Gallium can be incorporated into the framework of the zeolite (Col. 1, line 51); however, the zeolite catalyst employed in the process of the Short, et al. patent does not have the ZSM-5 framework structure.
U.S. Pat. No. 4,401,637 (Marosi, et al.) discloses a process for preparing olefins from methanol over a catalyst bed of a modified crystalline isotactic zeolite comprising framework gallium and an organic amine of low basicity. The catalysts employed in the process of the Marosi, et al. patent differ from ZSM-5 type catalysts.
U.S. Pat. No. 4,582,949 (Kieffer), incorporated herein by reference, discloses a two-stage conversion process for the preparation of aromatic hydrocarbons from olefins over metallosilicate catalysts. A crystalline gallium silicate catalyst having a silicon dioxide to gallium trioxide ratio of between 25 and 250 and a specific X-ray powder diffraction pattern is employed in the second stage.